Lead-in tape systems are commonly used to deliver signatures from a printing press to a stack. A lead-in tape system typically comprises a plurality of lead-in tape mechanisms spaced apart from one another and located side-by-side to one another to contact the signature across its width. Each lead-in tape mechanism has a lead-in tape on one side and a corresponding counter-rotating lead-in tape on the other side to form a signature passage, so that the signature is grasped on both sides and may be transported through the signature passage. Often the signature leaves the signature passage and enters a fan which receives the signature in a fan pocket. The signature is then delivered to a stack as the fan rotates. As described in U.S. Pat. No. 5,112,033, herewith incorporated by reference, it is often desirable to place two fans downstream from a single signature stream.
The lead-in tapes typically have guide rollers and a drive roller located inside the lead-in tape for guiding and driving the tape. There are guide rollers at the bottom of the lead-in tape where the signature exits, i.e. the exit rollers. In prior art devices, the side-by-side lead-in tape mechanisms have had exit rollers which are co-axial. In other words, the exit rollers are in-line and are the same height from one lead-in tape mechanism to the next side-by-side lead-in tape mechanism.
Also, the exit rollers on one side of a signature are often the same height as the exit rollers on the other side of the signature to ensure that the signatures exit straight.
There are several problems associated with having the exit rollers on one side of a signature the same height as the corresponding exit rollers on the other side of the signature. The even height of the exit rollers causes pounding between the exit rollers, since there is a heavy spring-loaded pressure between the exit rollers. Premature failure of the bearings, tapes or other components may occur, as well as fretting corrosion of the loaded components. Another problem associated with even height of the corresponding exit rollers is slippage of exit roller levers which hold the exit roller. Paper jams are more likely to occur between the heavily loaded exit rollers, which also may lead to lever slippage or premature failure of components. Moreover, the set up of the lead-in tape rollers is difficult because of the required precision to assure that the signatures are properly directed into the fan pockets.
It has therefore been found desirable to reduce the pressure on even height corresponding exit rollers by staggering them, i.e. having the exit roller on one side of a signature be higher or lower than the corresponding exit roller on the other side of the exit roller. This reduces the pressure between the exit rollers. However, the signatures are then often directed or deflected away to the side of the higher exit roller, which can cause problems, especially when a dual fan system is used, because the signatures should exit almost straight so that a signature is directed into the alternating fan pockets of the two fans. This problem is heightened because the thickness of a signature will effect the amount of the deflection when staggered exit rollers are used, therefore often making adjustments necessary when the thickness of the signature is changed.
In U.S. Pat. No. 5,112,033, the bottom rollers of two transport tapes 13 are fixed and slightly staggered, so that one exit roller is higher than its corresponding exit roller. However, the patent is directed to the fans and does not discuss the exit rollers.
U.S. Pat. No. 5,064,180 shows delivery of signatures through signature conveyor belts 14 and 15, the signatures being directly deposited into a stack.
U.S. Pat. No. 5,029,842 to Belanger et. al. discloses a signature delivery apparatus having six side-by-side signature lead-in tapes for delivering signatures to single fans. The exit rollers of the side-by-side lead-in tapes are coaxial about fixed axes.